Project Summary The purpose of Core 2 is to provide a centralized laboratory resource for processing, cryopreserving and distributing patient samples and to monitor the kinetics of immune reconstitution following allogeneic hematopoietic stem cell transplantation (HCT). Prior to transplantation, peripheral blood mononuclear cells (PBMC), bone marrow and serum or plasma are obtained from all patients enrolled on clinical trials supported by this Program Project. PBMC, plasma and serum are also obtained from normal stem cell donors. Following HCT, additional samples are obtained at regular intervals. All of these samples are processed, cryopreserved, entered into a computerized inventory and made available to Program investigators. Patient confidentiality is maintained at all levels and samples are only be obtained from patients who have provided informed consent. To support clinical trials and laboratory studies in each project, Core 2 also provides a series of phenotypic and functional immune assays that are used to monitor the effects of different immunologic interventions. Results of each of these assays are provided to Dr. Kim (Biostatistics ? Core 1) for correlation with laboratory studies in each project as well as with clinical outcomes.